Field of the Invention
Embodiments of the present invention relate to a sheet conveying device in an image forming apparatus such as a copying machine or a printer, and to an image forming apparatus including the sheet conveying device.
Description of the Related Art
In widely popular forming apparatuses such as an electrophotographic image forming apparatus, images are formed on sheets conveyed to an image forming section by a sheet conveying device. In such an image forming apparatus, sheets are fed out one by one from a feeding unit such as a sheet supplying cassette or a manual feeding tray, and are conveyed through sheet conveying paths. While the sheets pass through a transfer unit and a fixing unit during conveyance, images are formed on the sheets. A plurality of sheet conveying paths are provided to respond to selection of feeding units and selection of surfaces on which an image is to be formed, that is, one surface or both surfaces of each sheet, and merge into one sheet conveying path immediately before a registration roller pair that conveys the sheets to the transfer unit. In this conveyance merging part of the sheet conveying paths, a plurality of guide members overlap to merge the sheet conveying paths into one sheet conveying path.
However, to cope with the occurrence of a sheet jam (paper jam), such a conveyance merging part is required to have a structure in which an opening/closing mechanism is supported openably and closably relative to a main body of the device and jam recovery can be easily performed in a state in which the conveyance merging part is accessed and the conveying paths are opened by opening the opening/closing member when the sheet jam occurs. Japanese Patent Laid-Open No. 2006-282381 proposes a sheet conveying device in which jam recovery is performed in a conveyance merging part by opening an opening/closing member. In this structure, one of guide members overlapping to form the conveyance merging part is supported by the opening/closing member and the other guide member is fixed to a main body of the device by a latch. In this device, the guide member that supports rollers is held while being elastically biased toward the main body of the device on an inner side of the opening/closing member. This facilitates jam recovery operation, maintains the interval between the guide members, and positions the rollers with high accuracy.
With recent size reduction of image forming apparatuses, there is a conveyance merging part for duplex printing that is sharply curved by a large curvature immediately before a registration roller pair. For this reason, a sheet is not smoothly conveyed, and cannot properly enter the registration roller pair. This may cause folding of a leading edge portion of the sheet in a nip area between the registration roller pair, deviation of the sheet conveyance timing, or a sheet jam due to oblique conveyance. Japanese Patent Laid-Open No. 2004-354422 proposes a sheet conveying device in which a movable guide member (resin film) capable of pivoting and having a distal end in contact with a fixed guide member is disposed in a space between the fixed guide member and a registration roller pair. In this device, when a sheet is conveyed, it is corrected for skew by bending force of the movable guide member to optimize the entry of the sheet into the registration roller pair.
However, when the structure described in Japanese Patent Laid-Open No. 2006-282381 is complicated when applied to the section where a plurality of guide members overlap to form the conveyance merging part of the sheet conveying paths. For this reason, it is difficult to achieve both accurate positioning of the guide members and improved jam recovery performance with a simple structure. In the structure described in Japanese Patent Laid-Open No. 2004-354422, when jam recovery is performed in a state in which an opening/closing member is opened, the movable guide member interferes and hinders smooth jam recovery.